Needle Exchange

The contents of a needle exchange kit.

I found it interesting they include multiple needles of different bore sizes. The viscocity of drugs can be radically different, i.e. methadone is more viscous than heroin which is more viscous than cocaine. Pushing methadone through a small needle is impossible.

Here's a pipe pressure loss calculator to play with...
www.efunda.com/formulae/fluids/calc_pipe_friction.cfm#calc